Answer:
It will take 42 minutes.
Explanation:
In order to solve this we first have to calulate how long will it take one person to paint one wall:
54/6=9minutes
That is between 4 people it will take 9 minutes to paint a wall, one person alone supposing they all work at the same rate will take 36 minutes.
Now we just multiply that by the number of walls to be painted:
36*7=252
And we divide that by the number of people painting:
252/6=42
So it will take 42 minutes to paint 7 walls with 6 people painting.